Due to the large populations concentrated in many cities recently, it is difficult to obtain land. It is known that to utilize the land effectively it is probably advantageous to construct large scale buildings such as warehouses or garages, where human beings do not live, undersea or underwater.
According to conventional methods of constructing an underwater building, e.g., in constructing a large scale building such as a warehouse or a garage, after the building is constructed on the land it is carried by ship to a selected location and there sunk in the water. However, there is a problem in that the size of such a building is limited to one that can be carried by ship, and it takes a long time to set it up. Also, such a completed building can be transported only in calm weather and it is very difficult to sink a large building correctly since it must be set underwater horizontally. Also, it takes a long time and incurs high costs since a stable base must first be made underwater for the building.
Another known construction method requires setting up of boards underwater in a selected area to construct an underwater building, or dividing the area by piling stones. Thereafter, the inside water is drained, and an underwater building is constructed much as a building is constructed on land. By this method, the size of an underwater building is not limited and the underwater building can be constructed without concerns about the effect of water during the construction period. However, there is a problem in that the useful site is limited to a shallow place and it takes a long time and costs much to wall off the selected area, to drain the inside water, and to keep the construction situations the same as that on land.